[PATCH 15/17] powerpc/qspinlock: reduce remote node steal spins
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2022-07-28 06:41:37
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Allow for a reduction in the number of times a CPU from a different node than the owner can attempt to steal the lock before queueing. This could bias the transfer behaviour of the lock across the machine and reduce NUMA crossings. --- arch/powerpc/lib/qspinlock.c | 34 +++++++++++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/lib/qspinlock.c b/arch/powerpc/lib/qspinlock.c
index d4594c701f7d..24f68bd71e2b 100644
--- a/arch/powerpc/lib/qspinlock.c
+++ b/arch/powerpc/lib/qspinlock.c@@ -4,6 +4,7 @@ #include <linux/export.h> #include <linux/percpu.h> #include <linux/smp.h> +#include <linux/topology.h> #include <asm/qspinlock.h> #include <asm/paravirt.h>
@@ -24,6 +25,7 @@ struct qnodes { /* Tuning parameters */ static int STEAL_SPINS __read_mostly = (1<<5); +static int REMOTE_STEAL_SPINS __read_mostly = (1<<2); #if _Q_SPIN_TRY_LOCK_STEAL == 1 static const bool MAYBE_STEALERS = true; #else
@@ -39,9 +41,13 @@ static bool pv_prod_head __read_mostly = false; static DEFINE_PER_CPU_ALIGNED(struct qnodes, qnodes); -static __always_inline int get_steal_spins(bool paravirt) +static __always_inline int get_steal_spins(bool paravirt, bool remote) { - return STEAL_SPINS; + if (remote) { + return REMOTE_STEAL_SPINS; + } else { + return STEAL_SPINS; + } } static __always_inline int get_head_spins(bool paravirt)
@@ -380,8 +386,13 @@ static __always_inline bool try_to_steal_lock(struct qspinlock *lock, bool parav iters++; - if (iters >= get_steal_spins(paravirt)) + if (iters >= get_steal_spins(paravirt, false)) break; + if (iters >= get_steal_spins(paravirt, true)) { + int cpu = get_owner_cpu(val); + if (numa_node_id() != cpu_to_node(cpu)) + break; + } } spin_end();
@@ -588,6 +599,22 @@ static int steal_spins_get(void *data, u64 *val) DEFINE_SIMPLE_ATTRIBUTE(fops_steal_spins, steal_spins_get, steal_spins_set, "%llu\n"); +static int remote_steal_spins_set(void *data, u64 val) +{ + REMOTE_STEAL_SPINS = val; + + return 0; +} + +static int remote_steal_spins_get(void *data, u64 *val) +{ + *val = REMOTE_STEAL_SPINS; + + return 0; +} + +DEFINE_SIMPLE_ATTRIBUTE(fops_remote_steal_spins, remote_steal_spins_get, remote_steal_spins_set, "%llu\n"); + static int head_spins_set(void *data, u64 val) { HEAD_SPINS = val;
@@ -687,6 +714,7 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_pv_prod_head, pv_prod_head_get, pv_prod_head_set, " static __init int spinlock_debugfs_init(void) { debugfs_create_file("qspl_steal_spins", 0600, arch_debugfs_dir, NULL, &fops_steal_spins); + debugfs_create_file("qspl_remote_steal_spins", 0600, arch_debugfs_dir, NULL, &fops_remote_steal_spins); debugfs_create_file("qspl_head_spins", 0600, arch_debugfs_dir, NULL, &fops_head_spins); if (is_shared_processor()) { debugfs_create_file("qspl_pv_yield_owner", 0600, arch_debugfs_dir, NULL, &fops_pv_yield_owner);
--
2.35.1